BRAKE PRINCIPLE
Of all the systems that make car, the brake system might just be the most important. Its function is to retard or stop the motion of the vehicle which determine the safety of the driver, passenger and also pedestrian. The average driver uses the brakes about 75,000 times a year, making the brakes one of the most important (and overworked) parts of the car (McPhee, 2007). In the olden days it was also one of the simplest mechanisms in the vehicle. Over the years as improvements have been made, the system that has evolved is not simple anymore. When the brakes
are applied, the pads or shoes that press against the brake drum or rotor convert kinetic energy into thermal energy via friction. The cooling of the brakes dissipates the heat and the vehicle slows down. This is all to do with The First Law of Thermodynamics, sometimes known as the law of conservation of energy (Zammit, 1987). This law states that energy cannot be created nor destroyed; it can only be converted from one form to another. In the case of brakes, it is converted from kinetic energy to thermal energy.
Typically, there are two types of brake that are implemented in today’s car; Drum brake and disc brake. The brake is a device for slowing or stopping the rotation of a wheel of vehicles. To stop the wheel, friction material in the form of brake pads or shoe is forced mechanically, hydraulically, pneumatically or electromagnetically against both sides of the disc or drum which cause the wheel to slow or stop (Heinz, 2001).
When the brakes are used rapidly, the complete brake assembly will stay hot and get no chance to cool off. The brake cannot absorb much more heat because the brake components are already so hot. The braking efficiency is reduced thereby causing brake failure which could result in road accident. When the brake pedal is depressed, the vehicle’s braking system transmits the force from the driver’s foot to its brakes through a fluid. Since the actual brakes require a much greater force than the leg could apply with, vehicle must also multiply the force of foot. It does this in two ways; mechanical advantage (leverage) and hydraulic force multiplication. The brakes transmit the force to the tires using friction, and the tires transmit that force to the road using friction. The modern automotive brake system has been refined for over 100 years and has become extremely dependable and efficient.
Fig.1: Hydraulic braking system
Source: (Hesiler, 2001)
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